Sacroiliac Joint Implants And Implantation Methods

ABSTRACT

Sacroiliac (SI) joint implants for promoting SI joint fusion and methods of their delivery are described herein. The SI joint implant has a spacer operatively coupled to a planar member having tapered holes to receive fastening elements. When placed in the SI joint, the spacer engages the articular surfaces of the SI joint while the plate traverses the SI joint. The implant is held in place fastening elements, which are inserted through the tapered holes in the planar member. The implant is delivered via an inferior inlet MIS procedure, wherein the SI joint is accessed through an inlet inferior to the SI joint.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.14/518,667, filed Oct. 20, 2014, which claims priority to and thebenefit of U.S. Provisional Application Ser. No. 61/893,027 filed onOct. 18, 2013, the contents of which are hereby incorporated in theirentirety.

FIELD OF THE INVENTION

The present invention relates generally to surgical procedures for asacroiliac (SI) joint, and more specifically, to SI joint implants andminimally invasive surgical (MIS) procedures for delivering SI jointimplants.

BACKGROUND OF THE INVENTION

Sacroiliac (SI) joints are located between the sacrum and the right andthe left iliac bones, respectively. The SI joints provide support forthe entire weight of the upper body when a human stands erect, whichcreates a large amount of stress on the SI joints. Therefore, thesejoints are susceptible to injury and degeneration. Acute and chronicinjury, degeneration, and laxity of the supporting ligaments of the SIjoint can result in low back and radiating buttock and leg pain inafflicted patients. Stabilization or immobilization (fixation) of the SIjoint is commonly advocated as a surgical treatment for many SI jointdisorders.

A significant problem with certain conventional methods for SI jointfixation is that they require a surgeon to have direct access and a viewof the SI joint. Thus, some conventional SI joint fixation techniquesrequire the use of what is commonly referred to as “open surgery,” andresult in significant trauma and disruption to the tissues and skinsurrounding the SI joint. Open procedures increase the risk of damage tomajor nerves, blood vessels, ligaments, and muscles around the incisionsite. Moreover, open procedures increase operative, hospitalization, andrecovery time due to the extensive soft tissue damage resulting fromopen surgery techniques.

In response to the problems related to open surgery for SI jointfixation, minimally invasive surgical (MIS) procedures were developed.Currently, one of two approaches is taken to access the SI joint forfixation procedures: a lateral approach and a posterior approach. Inconventional MIS procedures employing the lateral approach, screws,rods, or other fixation devices are passed through a small incision (ascompared to that in open surgery) made on the lateral hip and insertedlaterally through the ilium, across the SI joint space, and into thesacrum. See, e.g. U.S. Pat. No. 8,221,428 by Trieu.

Alternatively, a posterior approach may be used to access the SI jointfor delivery of SI joint implants. See, e.g. U.S. Publication No.2012/0316565 by Stark and U.S. Publication No. 2013/0035723 by Donner.In the posterior approach disclosed by Stark and Donner a small (ascompared to that in open surgery) incision made in the patient's back,and the SI joint is accessed through an extra-articular recess locatedbetween the sacrum and the ilium.

Although the points of incision are different in current MIS proceduresfor accessing the SI joint, neither is truly minimally invasive.Conventional lateral MIS procedures still may result in significanttrauma to the major nerves, blood vessels, and muscle groups of the hip.While current posterior MIS approaches eliminate damage to the softtissues and neurovascular system of the lateral hip, they still carry asignificant risk of trauma to the spinal nerves and major back and hipligaments.

There exists a need for improved MIS procedures and devices that areless invasive and decrease soft tissue trauma and the risk toneurovascular tissue during SI joint fixation procedures.

Therefore, it is an object of the invention to provide an improved, lessinvasive method for implanting a fixation device in the SI joint.

It is further an object of the invention to provide an improved SI jointimplant device with decreased risk of trauma to surrounding tissuesduring implantation.

SUMMARY OF THE INVENTION

Implants for fixation of the SI joint, kits containing the implants, andmethods of using the implants and kits are described herein. In themethods, the sacroiliac (SI) joint implant is implanted in the SI jointusing a minimally invasive surgical (MIS) technique that accesses the SIjoint via an inferior inlet approach. The inferior inlet approachprovides a less invasive and safer approach for delivery of a SI jointimplant than current methods. Preferably, the SI joint implant includesa spacer operatively coupled to a planar member having tapered holes toreceive fastening elements. When delivered to the SI joint, the spacerengages the articular surfaces of the SI joint, which distracts the SIjoint providing stabilization of the hypermobile SI joints, while theplanar member traverses the SI joint providing static stabilization. Theimplant is fixed within the SI joint by fastening elements, which areinserted through the tapered holes of the planar member.

In one embodiment the spacer is operatively coupled to the planar memberin situ during an implantation procedure. In an alternative embodiment,the spacer is operatively coupled to the planar member ex vivo and isdelivered to the SI joint as a single unit. In further embodiments, theplanar member is curved so as to conform to the contour of the ilium.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1C show several views of one embodiment of a spacer configuredfor use in a SI joint implant.

FIGS. 2A-2C show several views of one embodiment of a planar memberhaving a tapered hole for use in a SI joint implant.

FIG. 3 shows one embodiment of a modular SI joint implant configured forin situ assembly.

FIGS. 4A-4D show several views of one embodiment of a SI joint implantassembled ex vivo.

FIG. 5A shows one view of a curved planar member.

FIGS. 5B and 5C show two different embodiments of the curved planarmember of FIG. 5A.

FIGS. 6A-6D show several views of one embodiment of a joint implantprior to affixing the SI implant within the SI joint. For clarity, theimplant is not shown within the SI joint.

FIGS. 7A-7D show several views of one embodiment of a joint implantafter affixing the SI implant within the SI joint. For clarity, theimplant is not shown within the SI joint.

FIG. 8 shows a lateral view of a hip region illustrating an approximatelocation of a SI joint implant within the SI joint.

FIG. 9 shows a posterior view of the hip region illustrating anapproximate location of a SI joint implant within the SI joint.

FIGS. 10A-10C show several views of one embodiment of a joint implanthaving a curved planar member. For clarity, the implant is not shownwithin the SI joint.

FIGS. 11A-11C show several views of one embodiment of a joint implanthaving a curved planar member and fixation elements placed throughtapered holes in the curved planar member. For clarity, the implant isnot shown within the SI joint.

FIG. 12 shows one embodiment of a spatula for preparing the SI jointspace.

FIG. 13 shows one embodiment of a box chisel for preparing the SI jointspace.

FIG. 14 shows the spatula of FIG. 12, with a handle removed, inside thebox chisel of FIG. 13, as would occur during preparation of the SI jointspace.

FIG. 15 shows one embodiment of a rasp for roughening the bone surface.

FIG. 16 is a posterior view showing the SI joint implants within the SIjoints.

FIG. 17 is a lateral view showing the approximate location of the SIjoint implant within the SI joint relative to the sacrum and spine.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion includes a description of a joint implantsystem, related components, and exemplary methods of employing theimplant system. Generally, FIGS. 1A-7D and 10A-11C illustrate severalembodiments of the disclosed SI implant system. FIGS. 8-9 and 16-17illustrate the use of the several embodiments illustrated in FIGS. 1A-7Dand 10A-11C in a patient in need of SI joint fixation. FIGS. 12-15illustrate exemplary tools for preparing the SI joint space forreceiving a SI joint implant. While several embodiments are described inconnection with these drawings, there is no intent to limit thedisclosure to the embodiment or embodiments illustrated therein.

I. Sacroiliac Implant System

The SI implant system has a spacer, which serves as a medium tostabilize and promote bone growth in the SI joint to promote SI jointfusion.

The spacer contains or is operatively coupled to one or more stabilizingelements. The spacer is operatively coupled to a planar member having atapered hole or holes. The planar member is fixed to the sacrum andilium and holds the spacer in place within the SI joint while new bonegrowth occurs. Although it is not a requirement, the planar member mayalso provide compression across the SI joint.

a. Spacer

The spacer 100 is an elongated member having a length (l.sub.s), aheight (h.sub.s), and a width (w.sub.s). An exemplary spacer is depictedin FIGS. 1A-1C. The spacer 100 has a first longitudinal axis (a.sub.s),which extends along the length (l.sub.s) of the spacer 100. The spacer100 serves as a medium for bone growth to promote fusion of the SIjoint.

The length (l.sub.s) of the spacer 100 ranges from approximately 30 mmto approximately 50 mm. The height (h.sub.s) of the spacer 100 rangesfrom approximately 15 to approximately 25 mm. The width (w.sub.s) of thespacer 100 ranges from approximately 6 mm and approximately 8 mm.Insofar as the SI joint is a longitudinal joint, it is not a requirementthat the spacer 100 conform exactly to the dimensions of the SI jointspace. In some embodiments, the spacer 100 may be smaller than the jointspace. In other embodiments the spacer 100 is substantially the samesize as the joint space. In yet further embodiments the spacer 100 maybe larger than the joint space. Most preferably the width (w.sub.s) ofthe spacer is approximately 2 mm larger than the width of a box chisel(1300, FIG. 13) that is used to prepare the SI joint space. A spacer 100that is wider than the prepared SI joint space provides a press-fit anddistracts the SI joint to increase stabilization of the SI joint.Preparation of the SI joint space is discussed in greater detail below.

Preferably, the spacer 100 is provided in three sizes: small, medium,and large, which can be provided together in a kit. Each size issuitable for use with patients of a particular range of body sizes. Forexample, the small spacer is suitable for use in people shorter thanapproximately 5′0″, the medium spacer is suitable for people betweenapproximately 5′0″ and 6′0″, and the large spacer is suitable for peopletaller than approximately 6′0″. Patient ranges for spacer sizes can bedetermined using other parameters, such as body weight and pelvis size.Preferably, the small spacer has a length (l.sub.s) of 20 mm, a height(h.sub.s) of 15 mm and a width (w.sub.s) of 8 mm. Preferably, the mediumspacer has a length (l.sub.s) of 25 mm, a height (h.sub.s) of 17 mm anda width (w.sub.s) of 8 mm. Preferably, the large spacer has a length(l.sub.s) of 30 mm, a height (h.sub.s) of 20 mm and a width (w.sub.s) of8 mm.

The spacer 100 typically has four sides 111 a, 111 b, 111 c, and 111 d,(collectively 111) of the spacer 100. In some embodiments, all foursides 111 are equal. In other embodiments, no two sides 111 are equal.Preferably, two sides (e.g. 111 a and 111 b) are equal to each other,but longer than the other two sides (e.g. 111 c and 111 d). In thisembodiment, the two shorter sides (e.g. 111 c and 111 d) are equal toeach other. See e.g. FIG. 1C.

In the preferred embodiment, the spacer 100 has a cavity 105. The cavity105 is configured to receive materials suitable for facilitating jointfusion. For example, bone graft material may be placed within the cavity105 to promote joint fusion. The cavity 105 creates spacer edges 106 a,106 b, 106 c, and 106 d (collectively 106) each having a thickness(t.sub.1-4).

Preferably, the cavity 105 is configured such that the cavity 105 ismaximized while not compromising the structural integrity of the spacer100.

In some embodiments, t.sub.1-4 are substantially equal to one another.For these embodiments t.sub.1-4 ranges from approximately 2 mm toapproximately 4 mm. In further embodiments, t.sub.1-4 vary such that notwo thicknesses are substantially the same. In these embodiments,t.sub.1-4 ranges from approximately 2 mm to approximately 6 mm.

In a preferred embodiment, t.sub.1 and t.sub.2 are substantially equal,ranging from approximately 2 mm to approximately 4 mm. Also in thepreferred embodiment, t.sub.3 and t.sub.4 are substantially equal,ranging from approximately 3 mm to approximately 5 mm.

In a preferred embodiment t.sub.1 and t.sub.2 are substantiallydifferent from t.sub.3 and t.sub.4. Most preferably, t.sub.1 and t.sub.2are less than t.sub.3 and t.sub.4, wherein t.sub.3 and t.sub.4 rangefrom approximately 3 mm to approximately 6 mm. This embodiment is shownin FIG. 1A.

i. Structural Surface Configurations

In some embodiments, a surface 108 a and 108 b (collectively 108) of thespacer 100 is configured to aid in SI joint fixation and implantintegration within the SI joint. For example, as shown in FIG. 1B, inone embodiment, opposing surfaces 108 of the spacer 100, which engagethe articular surfaces of the SI joint in vivo, are configured to haveridges 110 a, 110 b, 110 c (collectively 110). The ridges 110 may beuniform or may vary in width and depth along the length l.sub.s of thespacer 100. In other embodiments, the ridges 110 may be spikes or otherprojections out of the surface 108.

Further embodiments of the spacer 100 have a tapered edge 109. In someinstances the tapered edge 109 has a suitable shape and size to improveimplant fit within the SI joint. The taper may have structuralconfigurations, such as ridges 110.

In some embodiments, such as embodiments configured for in situassembly, the spacer 100 is operatively coupled to the planar member(FIG. 2A-2C) via an assembly element (FIG. 3, 303), preferably a camassembly. In these embodiments, the spacer 100 also has a first assemblyhole (FIG. 3, 301) that is preferably located on a short side (1111 c or111 d) of the spacer 100. Most preferably, the first assembly hole (301)is located on the first longitudinal axis a.sub.s, which is equidistantfrom either end (602 a and 602 b) of the short side (111 c or 11 d). Seee.g. FIGS. 6C and 6D. In other embodiments, the first assembly hole(301) is placed on a long side (111 a or 111 b) of the spacer 100. Onehaving ordinary skill will appreciate that the exact location of thefirst assembly hole (301) will depend on, inter alia, the jointinvolved, type of injury, and treatment desired. For example, theorientation of the spacer within the SI joint will determine if thefirst assembly hole is more appropriate on a short side (111 c or 111 d)or long side (111 a or 111 b) of the spacer 100.

Other structural surface modifications may be used as deemed necessaryor preferred. It will be appreciated by one having ordinary skill thatthe type of structural surface modification is dependent, inter alia,such as joint region involved, type of injury, and treatment desired.

ii. Bioactive Factors

A wide range of bioactive factors can be applied in the form of acoating or otherwise integrated into the surface of the spacer or planarmember to aid in SI joint fixation by inducing and supporting healing,repair and regeneration of soft and hard tissue, in particular, bone andcartilage. Suitable factors include, but are not limited to, autologousbone from ipsilateral posterior superior iliac spine, nucleotides,peptides, proteins, antibodies, biocompatible chemical compounds, andother pharmaceuticals. Preferred bioactive factors include parathyroidhormones (PTHs), platelet-derived growth factors (PDGFs), Transforminggrowth factor betas (TGF .beta.s), bone morphogenetic proteins (BMPs),vascular endothelial growth factor (VEGFs), Insulin-like growth factors(IGFs), Fibroblast Growth Factors (FGFs), and variants having the sameeffect in the human or animal body. Most preferred bioactive factorsinclude autologous bone graft, PDGF AB, PTH.sub.1-34, BMP2, BMP 7,TGF.beta.1, TGF.beta.3, VEOF 121, and VEGF 110. Other suitable bioactivefactors include, but are not limited to, antibiotics, chemotherapeutics,analgesics, anesthetics, anti-proliferating agents, andimmunomodulators.

a. Planar Member

i. Straight Planar Member

Given the irregular and substantially curved structure of the sacrum andthe ilium on either side of the SI joint, a substantially straightplanar member (planar member) is preferably configured so as to preventundesired contact with the sacrum or ilium. Thus, preferably a planarmember is just large enough to accommodate two tapered holes.

FIGS. 2A-2C show several views of one embodiment of a planar member 200having a tapered hole 201 for use in a SI joint implant. In oneembodiment, the planar member 200 has a length (l.sub.p) along a secondlongitudinal axis (a.sub.pl), a height (h.sub.p), and a width (w.sub.p).In the preferred embodiment, the planar member 200, has two taperedholes 201 a and 201 b (collectively 201) for receiving a fasteningelement (601 a and 601 b, collectively 601, FIG. 6). Other embodimentscontain additional holes 201, if additional fastening elements (601) areused. One having ordinary skill will appreciate that the number offastening elements required depends on, inter alia, the joint involved,type of injury, and treatment desired. The tapered holes may be off-setfrom one another so as to decrease the length (l.sub.p) of the planarmember 200.

As shown in FIG. 2C, the tapered hole 201 is tapered along the width(w.sub.p) of the planar member 200. Thus, the first opening of thetapered hole 201 on a top surface 206 of the planar member 200 is largerthan the second opening of the tapered hole on a bottom surface 207 ofthe planar member 200. The tapered hole 201 has any suitable shape,including but not limited to, substantially circular, elliptical,oblong, irregular, and rectangular. Preferably, the tapered hole 201 isoblong. Preferably, the diameter of the tapered hole is approximately 4mm to approximately 6 mm. By way of example, the planar member 200 canbe an AO Foundation compression plate.

In some embodiments, such as embodiments configured for in situassembly, the planar member 200 is operatively coupled to the spacer 100(FIG. 1A-1B) via an assembly element (303), preferably a cam assembly.In these embodiments, the planar member 200 also has a second assemblyhole (FIG. 3, 302) that is preferably located on the planar member 200such that it is centered along a horizontal axis a.sub.ph and extendsthrough the entire width w.sub.p of the planar member 200. For allembodiments, the second assembly hole (302) is located at any positionalong the second longitudinal axis a.sub.pl that is not occupied by atapered hole 201. See e.g. FIG. 3.

One having ordinary skill will appreciate that the exact location of thesecond assembly hole (302) will depend, in part, on the number offastening elements (601) required. The number of holes is equivalent tothe number of fastening elements (601).

ii. Curved Planar Member

FIGS. 5A-5C shows several views of a curved member having a tapered holefor use in a SI joint implant. The sacrum and ilium are substantiallyirregular in shape and contour. In particular, they both have asubstantial curve in the bone in close proximity of the SI joint. Thispresents challenges for affixing implants in this region. Thus, in someembodiments, the SI joint implant is a curved planar member 500 thatmatches the contour of the ilium. In other embodiments, the curvedplanar member 500 matches the contour of the sacrum. To match thecontour of the sacrum, the curved planar member 500 has a curve rangingfrom approximately 30 degrees to approximately 40 degrees. In furtherembodiments, the curved planar member is substantially curved so as tomatch the contour of both the sacrum and the ilium.

FIG. 5A shows a lateral view of one embodiment of a curved planar member500 having a tapered hole 503 for use in a SI joint implant. The curvedplanar member 500 has a first section 501 and a second section 502residing on either side of an apex 504 of the curved planar member 500.In short, the shape of the curved planar member 500 is configured tosubstantially conform to the shape of the ilium and/or sacrum.

FIGS. 5B and 5C are two different embodiments of the curved planarmember 500 of FIG. 5A. The embodiment depicted in FIG. 5B contains twoor more tapered holes 503 a and 503 b (collectively 503), while theembodiment depicted in FIG. 5C contains only one tapered hole 503.

The embodiment illustrated in FIG. 5B has a curved planar member 500having tapered holes 503 located in the second section 502 along a thirdlongitudinal axis a.sub.cl. The third longitudinal axis a, is analogousto the second longitudinal axis (a.sub.pl, FIGS. 2A and 2B) of theplanar member (200, FIGS. 2A-2C). To reduce slipping within the jointand thereby ensure that the curved planar member 500 remains in placefollowing other manipulations, in some embodiments, the curved planarmember 500 includes structural features 506 such as ridges, teeth, orother surface projections. One having ordinary skill will appreciatethat the location and type of structural features will depend in interalia, the joint involved, type of injury, and treatment desired.

In some instances, it is preferable to minimize the number of fasteningelements required to affix the implant to the bone. For example, incases where the patient's bone has reduced density due to osteoporosis,it may be advantageous to minimize the use of pre-drilled burholes topreserve bone integrity. FIG. 5C shows another embodiment of a curvedplanar member 500 having only one tapered hole 503. In this embodiment,a single tapered hole 503 is located along the third longitudinal axisa.sub.cl of the second section 502 of the curved planar member 500. Thefirst section 501 of the curved planar member 500 has surfacemodifications 506 to engage the ilium and prevent slipping of theimplant.

b. Fixation Components

In operation, the SI joint implant is secured within the SI joint by oneor more, typically two or more, fastening elements (601 a and 601 b,collectively 601) inserted through the tapered holes 201 of the planarmember 200 to fixate the implant within the joint space. See FIG. 6. Thefastening element is any suitable element for attaching a planar member200 to a bone, such as a screw, nail, or rod. Preferably, the fasteningelements are titanium bone screws. The bone screws can be of anystandard type, but are preferably type HA. The bone screws can beself-tapping, cannulated, low-profile, hex-head, flat-head, or be of anyother suitable type. In other embodiments, the fastening elements aremade of any suitable biocompatible material, including non-biodegradableand biodegradable materials. In other embodiments the fastening elementsare pins, rods, or other suitable structure for fixating the implantwithin the joint space.

c. Materials and Method of Manufacture of SI System

The various components of the SI implant system are fabricated frombiocompatible materials suitable for implantation in a human body,including but not limited to, metals, synthetic polymers, ceramics,and/or their combinations, depending on the particular applicationand/or preference of a medical practitioner. Further, the components ofthe implant system can be manufactured via various methods. For example,the spacer or planer member may be manufactured and assembled viainjection-molding, insert-molding, co-extrusion, pultrusion, transfermolding, overmolding, compression molding, 3-Dimensional printing,dip-coating, spray-coating, powder-coating, porous-coating, milling froma solid stock material and their combinations.

i. Spacer and Planar Member

The spacer 100 and planar member 200 can be fabricated frombiocompatible materials such as commercially pure titanium, titaniumalloys, Grade 5 titanium, super-elastic titanium alloys, cobalt-chromealloys, stainless steel alloys, superelastic metallic alloys (e.g.nitinol, super elasto-plastic metals, such as GUM METAL®), carbon fiber,thermoplastics such as polyaryletherketone (PAEK), includingpolyetheretherketone (PEEK) and polyetherketone (PEK), carbon fiberreinforced PEEK composites, PEEK-BaSO.sub.4 composites, ceramics andcomposites thereof, such as calcium phosphate (e.g. SKELITE™), rigidpolymers including polyphenylene, polyamide, polyimide polyetherimide,polyetherimide, polyethylene, polyurethanes of any durometer, epoxy, orsilicone. Different components of the SI implant system may befabricated from a heterogeneous material, such as a combination of twoor more of the above described materials to achieve various desiredcharacteristics such as strength, rigidity, elasticity, compliance,biomechanical performance, durability and radiolucency or imagingpreference.

ii. Fixation and Assembly Elements

The fixation elements 601 and assembly elements 303 can be fabricatedfrom biocompatible materials titanium, titanium alloys, Grade 5titanium, super-elastic titanium alloys, cobalt-chrome alloys, stainlesssteel alloys, superelastic metallic alloys (e.g. nitinol, superelasto-plastic metals, such as GUM METAL®), stainless steel, carbonfiber or combinations thereof.

iii. Cavity Filler

In embodiments having a spacer cavity, the spacer cavity may be filledwith suitable biocompatible materials to facilitate joint fixation orfusion. Suitable biocompatible materials include, but are not limited tobone material including autograft, allograft, xenograft or transgeniccortical and/or corticocancellous bone, and tissue growth ordifferentiation factors, partially resorbable materials, such ascomposite of metals and calcium based ceramics, composites of PEEK andcalcium based ceramics, composites of PEEK with resorbable polymers,totally resorbable materials, such as calcium based ceramics such ascalcium phosphate, tri-calcium phosphate (TCP), hydroxyapatite (HA)-TCP,calcium sulfate, or other resorbable polymers such as polylactide,polyglycolide, polytyrosine carbonate, and their combinations.

II. Configuration of the SI Joint Implant System in Use

a. Modular SI Joint Implant System

FIG. 3 shows one embodiment of a modular SI joint implant configured forin situ assembly. For some SI joint procedures, it is preferable thatthe SI joint implant, which is a single unit in situ, be introduced tothe joint one component at a time and operatively coupled togetherduring the procedure to form the SI joint implant system. In situationswhen direct access to the SI joint is limited because small incisionsare used, the ability to introduce components separately into the SIjoint is particularly useful. In some embodiments, the SI joint implantis a modular implant system 300. The components of the modular SI jointimplant system can be supplied as a kit.

During an implantation procedure of a spacer/planar implant, the medicalpractitioner inserts one component of the modular SI joint implantsystem 300 at a time into the SI joint and then operatively couples thespacer 100 to the planar member 200 in situ.

First, the spacer 100 is first delivered into the SI joint space. Thespacer 100 is orientated such that the first assembly hole 301 is in asuitable position within the SI joint space to receive the assemblyelement 303. Then, the planar member 200 is delivered to the SI jointspace and orientated such that the planar member 200 traverses the SIjoint and the second assembly hole 302 aligns with the first assemblyhole 301. The assembly element 303 is then passed through the secondassembly hole 302 into the first assembly hole 301, thereby operativelycoupling the planar member 200 and the spacer 100. When fully assembledin situ, the first longitudinal axis a.sub.s of the spacer 100 isnon-parallel, preferably substantially perpendicular, to the secondlongitudinal axis a.sub.pl of the planar member 200. See e.g. FIG. 4B.

In further embodiments, the spacer 100 and the planar member 200 are notoperatively coupled to one another in situ. The spacer 100 is insertedinto the SI joint space and is held in place during the procedure by asuitable device. The planar member 200 is then placed in the SI joint,such that it traverses the SI joint. When fully fixed to the sacrum andthe ilium it is expected that the planar member 200 will move the sacrumand ilium closer to one another, thus collapsing the SI joint spacearound the spacer 100. This compression of the SI joint space in theseembodiments will be at least sufficient to hold the spacer 100 withinthe SI joint space until new bone growth in the SI joint space occurs.

b. Pre-Assembled SI Joint Implant System

There are also circumstances in which a pre-assembled implant system isdesired. FIGS. 4A-4D show several views of one embodiment of an SI jointimplant assembled ex vivo, i.e. assembled prior to implantation(referred to herein as “pre-assembled”). In one embodiment of apre-assembled SI joint implant 400, the spacer 100 and the planar member200 are operatively coupled at a joint 401 such that the firstlongitudinal axis a.sub.s of the spacer 100 is non-parallel, preferablysubstantially perpendicular, to the second longitudinal axis a.sub.pl ofthe planar member 200.

Preferably, the joint 401 is substantially centered along the horizontalaxis a.sub.ph of the planar member 200. See e.g. FIG. 4A. In otherembodiments, especially in those in which the tapered holes 201 arestaggered, the joint 401 can be at any position along the horizontalaxis a.sub.ph of the planar member 200. In all embodiments the joint 401may be located at any position along the second longitudinal axisa.sub.pl of the planar member that is not occupied by a tapered hole201.

As shown in FIGS. 4C and 4D, preferably the joint 401 is formed from ajoint fastener extending from the planar member 200 to a second receiveron the spacer 100. In further embodiments, the joint 401 is formed froma joint fastener extending from the spacer 100 to a first receiver onthe planar member 200. In yet another embodiment, the joint 401 isformed by fusing the spacer 100 and the planar member 200 together, suchthat joint has no clear demarcation between the spacer 100 and theplanar member 100. Thus, for these embodiments, the spacer 100 and theplanar member 200 form one cohesive unit.

c. Curved SI Joint Implant

Like the embodiments employing a straight planar member 200, embodimentsof the SI joint implant system employing a curved planar member 500 canbe modular or pre-assembled, as previously described. When the spacer100 and curved planar member 500 are operatively coupled, the curvedplanar member 500 is oriented such that its longitudinal axis (a.sub.t)is non-parallel, preferably substantially perpendicular, to thehorizontal axis (a.sub.hp) of the spacer 100. See e.g. FIGS. 10A-10C. Asshown in FIGS. 11A-11C, fixation elements 601 can be inserted throughthe tapered holes 503 of the curved planar member 500 and into the bonesof the sacrum and ilium to secure the curved planar member 500 andspacer 100 within the SI joint.

III. Fixation of the SI Joint Implant within the SI Joint

In use, a fastening element 601 is placed through each tapered hole 201into pre-drilled burholes in the bones of the patient's SI joint. Theseburholes are drilled off-center relative to the location of thecorresponding tapered hole 201. As the fastening element is insertedwithin the bone of a patient (e.g. when a screw is being tightened), thetapering of the tapered hole 201 forces the fastening element 601 tomove from an initial position to a final position that is substantiallydisplaced from the initial position and towards the spacer 100,preferably resulting in compression of the SI joint space. This actionis sometimes referred to as dynamic compression. This process isdiscussed in greater detail with reference to FIGS. 6A-7D.

Methods of stabilizing the SI joint employing rods, screws, or otherdevices that are inserted laterally through the hip and traverse the SIjoint do not typically induce significant bone growth across the SIjoint space so as to fuse the joint. Here, the SI joint implant promotessignificant bone growth across the SI joint so as to result in fusion ofthe joint as opposed to merely stabilization. Any compression providedby the action of the fastening element 601 within the planar member 200further promotes in new bone growth across the SI joint and furtherstabilizes the SI joint.

a. Initial Position of Fixation Components

FIGS. 6A-6D illustrate one embodiment of a fully assembled SI jointimplant prior to affixing the SI implant within the SI joint. Turningfirst to FIGS. 6A and 6B, the method of fixing the SI joint implantwithin the SI joint begins by first inserting fastening elements 601through the tapered holes 201 into pre-drilled boreholes in thepatient's bone. The boreholes are placed in the patient's bone such thatthey are substantially off-center relative to the location of thecorresponding tapered holes 201 (503) of the planar member 200 (curvedplanar member 500). Preferably, the location of the boreholes, relativeto the tapered holes 201, is distal to the spacer 100 or second assemblyhole (FIG. 3, 302). Thus, when the fastening elements 601 are initiallyplaced through the tapered holes 201 (503) into the boreholes, thefastening elements 601 are off-center within the tapered holes 201 (503)of the planar member 200 (curved planar member 500). See e.g. FIGS.6A-6B.

As illustrated in FIGS. 6B through 6D, the fastening elements 601 arepreferably positioned such that they are substantially parallel to thespacer 100. However, the fastening elements 601 can have any angle themedical practitioner deems necessary or prefers. One having ordinaryskill will appreciate that this will depend on, inter alia, the jointinvolved, type of injury, and treatment desired.

The holes for the screws can be prepared with the conventional steps of:perforating the cortical bone, for example using an awl or burr,drilling the bone to create a screw trajectory for the tap; tapping thebone as deep as needed to help drive the screw; and implanting thescrews.

b. Final Position of Fixation Components

The final position of the fastening elements 601 is depicted in FIGS.7A-7D. In use, the medical practitioner completely inserts, or sets, thefastening elements 601 in the bones of the SI joint. As the fasteningelements 601 are finally set into the bone, they move from their initialposition (illustrated, e.g., in FIGS. 6A and 6B) within the taperedholes 201 to their final position, which is preferably substantiallycentered within the tapered holes 201. This final configuration is shownin FIGS. 7A and 7B. Thus, as the fastening elements 601 are set into thebone, the taper of the tapered holes 201 forces the fastening elements601 into a final position that is closer to the joint space, moving thefastening elements 601 closer together.

IV. SI Joint Implant Delivery

The inferior inlet approach disclosed herein may be used to deliver anySI joint implant or other device to the SI joint or SI joint region.Preferably, the inferior inlet approach is used to deliver the SI jointimplants disclosed herein to an SI joint of a patient in need thereof.FIG. 8 shows a lateral view of a hip region illustrating an approximatelocation of an SI joint implant within the SI joint.

For delivery of the SI joint implant, the patient is preferably placedin a prone position. If desired, fluoroscopy is used to visualize the SIjoint according to methods well established in the field. Preferably,the position of the fluoroscopy is an inlet view of the pelvis with anapproximately 10-15 degree angle to isolate the affected SI joint. Thisview provides a medical practitioner with a straight view of the SIjoint.

A medical practitioner then accesses the SI joint through an incision inthe skin and soft tissue of a patient. The incision may be of any size,but preferably the incision is less than one inch. The incision is madein a region 803 below the back of a patient. Preferably, the incision ismade in alignment with the longitudinal axis of the SI joint. The angle804 of a trajectory 805 of the inferior inlet approach is less than 90degrees.

After the incision is made, a guide wire, such as a K-wire, is insertedthrough the incision and advanced until it reaches the SI joint. Theguide wire is used to guide the surgical instruments to the desiredsite.

Optionally, one or more dilators are fed along the K-wire to push softtissue aside. For example, a dilation system having a plurality oftubular members that can be concentrically disposed may be used. First,a smallest first tubular member is fed over the guide wire so that adistal end of the first tubular member is advanced into the surgicalsite. As the distal end advances into the incision, the tissuesurrounding the first tubular member is radially outwardly retracted ordilated.

Once the first tubular member is inserted to a desired depth, a slightlylarger second tubular member is pushed over the second tubular memberand into the tissue so as to further dilate the tissue. This process isrepeated for additionally larger tubular members until the tissue at thesurgical site is retracted to a desired extent to facilitate thesurgical procedure.

After reaching the desired width, all of the inner dilators are removed,while the outermost tubular member (dilator) remains in place, definingthe opening through which the other surgical instruments will beinserted.

The various instruments that are used to prepare the SI joint increasein width, with the smallest instrument used initially and the largestinstrument used prior to insertion of the SI joint implant. For example,for an implant that is 6 mm in width, the instruments may progressivelyincrease in width starting with an instrument of about 3 mm in width andending with an instrument that is about 5.75 mm in width, this allowsfor a press fit (or friction fit) of the implant to the bone afterpreparation of the SI joint.

A spatula 1200 having a handle 1201 and a spatula end 1202 is placedwithin the incision and fed along the guide wire into the inferioraspect of the SI joint in alignment with the longitudinal axis of the SIjoint. In one embodiment, the handle is removed. The spatula may haveany suitable dimensions, but preferably is approximately 20-30 mm inlength, 15-20 mm in height, and about 3-4 mm in width, preferably 3.5 mmin width. Preferably, the spatula 1200 has a stop 1203 placed in asuitable location to prevent over insertion of the spatula 1200 withinthe SI joint. Preferably, the spatula has a suitable configuration toguide the box chisel over the shaft of the spatula and prevent rotationof the box chisel relative to the spatula. Typically, the shaft of thespatula is rectangular.

Once the spatula 1200 is placed within the SI joint, the removablehandle 1201 is detached, leaving the spatula end 1202 and the stop 1203,if present, at the inferior aspect (FIG. 16, 1500) of an SI joint. Asshown in FIGS. 13 and 14, a box chisel 1300 is then placed over thespatula end 1202. The box chisel preferably includes a hollow portionalong the length of the chisel, which mates with the configuration ofthe shaft of the spatula. This allows the chisel to slide along thelength of the spatula without rotation to the desired site. The chiselhas suitable dimensions for fitting in the SI joint. Typically the tipof the chisel has a width of about 5-6 mm, preferably 5.5 mm.Preferably, the chisel also contains a window (or opening) at itsproximal tip region. This opening is configured for graft retrieval.

The box chisel is then manipulated by the surgeon to removecartilaginous/fibrous tissue on either side of the SI joint. Thisresults in a suitable environment for bone growth to promote fusion ofthe SI joint. Using this combination of the spatula 1200 and the boxchisel 1300 as described herein, results in equal thickness of jointspace on either side of the spatula.

It may be difficult to remove the box chisel from the SI joint.Optionally a mallet or slap hammer is used to apply an impacting forceon the box chisel and loosen it from the site to aid in its removal.Optionally, the distal end of the box chisel is configured forattachment to a slap hammer.

Slap hammers typically consist of a guide rod and a sliding weight. Oneend of the guide rod is affixed to an object or surface, such as a boxchisel (or any other surgical tool that requires removal). The slidingweight may be thrown upward, generating a jerking force when the slidingweight strikes a stop on the end of the guide rod. The sliding weightmay be repeatedly “thrown” to extract the surgical implement.

If desired, a rasp, or other suitable device, can be used for additionalpreparation of the SI joint space. The rasp may be used to roughen thebone surface to prepare for fusion. An exemplary rasp 1500 isillustrated in FIG. 15. Typically the tip 1502 of the rasp has a widthof about 5-6 mm, preferably 5.75 mm. Optionally, the distal end of therasp is configured to attach to a slap hammer.

Optionally, loose debris within the SI joint space is removed. Forexample pituitary ronguer, or other suitable device, may be used toremove loose debris from the SI joint prior to insertion of the SI jointimplant.

Preferably, the prepared SI joint space resulting from use of the boxchisel 1300 and other optional devices is approximately 2 mm smallerthan the width of the spacer 100. This provides a press-fit anddistraction of the SI joint leading to further stabilization of the SIjoint by reducing micromotion. The prepared SI joint space is at leastthe length of the spacer 100.

a. Delivery of a Modular SI Joint Implant

For a modular SI joint implant 300, the spacer 100 is inserted withinthe prepared SI joint space at the inferior aspect 1500 of the SI joint,such that the spacer 100 engages the articular surfaces of the SI joint.See e.g. FIG. 16. This is followed by placement of the planar member 200(or 500) along the inferior aspect 1500 of the SI joint as shown in FIG.16. Fixation elements 601 are then inserted through the tapered hole orholes 503 in the planar member 200 (or 500). The fixation elements 601are inserted along the longitudinal axis of the SI joint (a.sub.SIl)without encroaching on the neural foramen of the sacrum, as shown inFIG. 16. In some embodiments, the planar member 200 (or 500) isoperatively coupled to the spacer 100 via the assembly element aspreviously described prior to insertion of the fixation elements throughthe tapered holes 503. In other embodiments, coupling of the planarmember 200 (or 500) and the spacer 100 via the assembly element 303occurs after the fixation elements 601 have been inserted through thetapered holes 303 into the bones. In other embodiments, the spacer 100and planar member 200 (or 500) are not operatively coupled together, aspreviously described. In these embodiments, the spacer 100 is heldwithin the SI joint space by the press-fit of the spacer 100 within theSI joint space and/or compression on the SI joint space provided by thedynamic compression action of the planar member 200 (or 500).

b. Delivery of a Pre-Assembled SI Joint Implant

For the pre-assembled SI joint implant, the pre-assembled SI jointimplant is delivered to the prepared SI joint space, such that thespacer 100 is within the SI joint space, and the planar member 200, 500traverses the SI joint along the inferior aspect 1500 of the SI joint.See e.g. FIGS. 15 and 17. Fixation elements 601 are then insertedthrough the tapered hole(s) 503 of the planar member 200, 500 and intothe bones. The fixation elements 601 are inserted such that they arealigned with the longitudinal axis of the SI joint without encroachingon the neural foramen of the sacrum.

The inferior inlet approach provides access to the inferior aspect 1500of the SI joint while avoiding the nerves exiting the sacrum, as well asthe majority of blood vessels, ligaments, and muscles supporting the hipand lumbar region of a patient. Further, the inferior inlet approachallows for smaller incisions than the current MIS techniques foraccessing the SI joint. Therefore, the inferior inlet approach reducesrecovery time, risk of complications from surgery, and reducesvisibility of the incision once healed.

FIG. 9 shows a posterior view of the hip region illustrating anapproximate location of a SI joint implant within the SI joint. Asillustrated in FIG. 9, the trajectory 805 of the inferior inlet approachallows key elements of the vascular, nervous, and musculoskeletal systemto be avoided. In one embodiment, the SI joint implant is placed orassembled within the prepared SI joint space 807 at the inferior aspect1500 of the SI joint, such that the spacer 100 engages the surface ofthe sacrum and the ilium. Moreover, the planar member 200 (or 500)traverses the SI joint such that the implant may be affixed to thesacrum and the ilium through the tapered holes 201 as previouslydescribed. The alignment of the SI joint implant at the inferior aspect1500 of the SI joint is shown in greater detail with respect to thesacrum and spinal column in FIG. 17.

Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of skill in the artto which the disclosed invention belongs. Publications cited herein andthe materials for which they are cited are specifically incorporated byreference.

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, many equivalents to the specificembodiments of the invention described herein. Such equivalents areintended to be encompassed by the following claims.

1.-23. (canceled)
 24. A method for delivering a sacroiliac joint implantto an inferior aspect of a sacroiliac joint (SI) located between asacrum and an iliac bone, the method comprising: making an incision inthe inferior posterior lumbosacral region of a patient; inserting aninstrument suitable for preparing a joint space through the incision andinto the SI joint through the inferior aspect of the SI joint along aninferior insertion direction; and delivering a SI joint implantincluding a curved planar member and a spacer coupled to the curvedplanar member to the inferior aspect of the SI joint, the curved planarmember having a first section and a second section that is curved withrespect to the first section and toward the spacer member, such that,the spacer is disposed in the joint space along the inferior insertiondirection and the curved planar member conforms to a portion of thesacrum or the iliac bone.
 25. The method of claim 24, wherein theincision is approximately one inch or less.
 26. The method of claim 24,wherein the spacer comprises a first longitudinal axis and two opposingsurfaces, wherein the two opposing surfaces extend along the firstlongitudinal axis; wherein the spacer is operatively coupled to thecurved planar member comprising a tapered hole and a second longitudinalaxis, wherein the curved planar member is operatively coupled to thespacer such that the second longitudinal axis is non-parallel, to thefirst longitudinal axis; and wherein the implant is aligned within thejoint space such that the opposing surfaces of the spacer engage both ofthe opposing articular surfaces of the sacroiliac joint and the curvedplanar member traverses the inferior aspect of the sacroiliac joint. 27.The method of claim 24, wherein the instrument and the SI joint implantare delivered to the inferior aspect of the SI joint at an angle of lessthan 90 degrees.
 28. The method of claim 26, wherein the curved planarmember further comprises a second tapered hole.
 29. The method of claim28, further comprising inserting a fastening element into the taperedholes.
 30. The method of claim 29, wherein the fastening element isselected from the group consisting of a screw, a nail, a pin, a rod, andcombinations thereof.
 31. The method of claim 29, wherein an initialposition of the fastening element is off-center within the taperedholes.
 32. A method for delivering a sacroiliac joint implant to aninferior aspect of a sacroiliac joint (SI) located between a sacrum andan iliac bone, the method comprising: making an incision in an inferiorposterior lumbosacral region of a patient; inserting an instrumentconfigured to prepare a joint space through the incision and into the SIjoint through the inferior aspect of the SI joint and along an inferiorinsertion axis that extends at least partially along aninferior-superior direction, wherein the inferior-superior direction isperpendicular to a posterior-anterior direction; and delivering a SIjoint implant that includes a spacer through the incision along theinferior insertion axis into the inferior aspect of the SI joint, suchthat, the spacer is disposed in the joint space between the sacrum andthe iliac bone along the inferior insertion axis.
 33. The method ofclaim 32, wherein the incision is approximately one inch or less. 34.The method of claim 32, wherein the spacer extends along a firstlongitudinal axis, the spacer further defining two surfaces disposed onopposite sides of the first longitudinal axis, wherein in the deliveringstep, the spacer is disposed within the joint space such that a) theopposing surfaces of the spacer engage opposing articular surfaces ofthe sacrum and iliac bone, and b) the first longitudinal axis issubstantially aligned with of inferior insertion axis.
 35. The method ofclaim 32, wherein the inferior insertion axis is inferiorly offset withrespect to a posterior-inferior direction.
 36. The method of claim 32,wherein the instrument and the SI joint implant are delivered to theinferior aspect of the SI joint wherein along the inferior insertionaxis that is disposed at an angle of less than 90 degrees.
 37. Themethod of claim 32, wherein the spacer is operatively coupled to aplanar member that extends along a second longitudinal axis, the planarmember including at least one tapered hole, wherein the secondlongitudinal axis is non-parallel to the first longitudinal axis,wherein in the delivering step the planar member traverses the inferioraspect of the sacroiliac joint.